The present invention relates to a process for the preparation of hydroxyethylcyclohexanes which can optionally contain a nitrogen atom in the hexane ring by catalytic hydrogenation of the corresponding hydroxyethylbenzenes or hydroxyethylpyridines.
Hydroxyethylcyclohexanes and hydroxyethylpiperidines are intermediates for the preparation of pharmaceuticals, fragrances and insect repellents.
When hydroxyethylcyclohexanes and hydroxyethylpiperidines are prepared using customary hydrogenation catalysts such as Raney nickel or rhodium and/or in polar solvents by hydrogenation of the corresponding hydroxyethylbenzenes or hydroxyethylpyridines, secondary reactions take place to a considerable extent, which lead to the formation of undesired byproducts. There is therefore a need for a process which can be used to prepare hydroxyethylcyclohexanes which can optionally contain a nitrogen atom in the cyclohexane ring in good selectivities of, for example, greater than 95%.
We have now found a process for the preparation of hydroxyethylcyclohexanes which can optionally contain a nitrogen atom in the cyclohexane ring by catalytic hydrogenation of the corresponding hydroxyethylbenzenes or hydroxyethylpyridines which is characterized in that ruthenium which has been treated before use with a reducing agent is used as catalysts.